Smoothing out the tables?

[super_kev]

So, I'm looking through here and reading many threads on tuning and there are many mentions of smoothing the tables, when it relates to timing, throttle pedal/pedal map, and fueling. Are you folks just looking at three cells at a time and picking the middle one to be between both side values?

Looking at one of the two Pedal Maps (Transient, Steady State) I see that the value (2007 5.9 ECM) for 25% accelerator pedal goes from 33.2 (600rpm) to 30 (650rpm), 28.3 (750rpm), 23.2 (800rpm), 23.2, 23.2 (1000rpm), jumps to 30 at 1200rpm, then 30 and finally 35 (1500-3000rpm). So are you folks making, say, the 650-900rpm values 30.0, and 1000rpm and up at 35.0? Is that considered smoothing? Is there a reason why the pedal drops to 23.2 in the idling range? Is this to allow for more finesse of the throttle, and more travel/movement to better control takeoff?

For the timing tables (Main SOI/Transient for example) or fueling (Main Inj Pulsewidth), do you use the Smooth Selection or Smooth Between Horizontal or Vertical Bounds buttons to start? The timing changes in various parts of the table so I wouldn't want to smooth the entire table at once, but from where to where to folks usually go? I'm sure the smoothing buttons are there for a reason, but should they be used?

Thanks for the feedback.

[Jim P]

With your throttle maps if you adjust them just make them linear, 0%-0mm3, 25%-36.24mm3, 75%-72.49mm3, 100%-144.97mm3. You probably won?t actually notice any difference either way.

The way the throttle map works is this as best as I know, for a given throttle percent it will reference to one of those two maps and look up the desired mm3 command, it will then check that desired mm3 command against all fuel limit tables and the torque table. If there isn?t any limits being placed on the desired mm3 command it will then use the current rpm and desired mm3 command to look up the commanded rail pressure. Once it has the commanded rail pressure it will use that rail pressure command and mm3 command to look up the duration required for the commanded mm3 and rail pressure.

Why I say you probably won?t notice any difference either way is that the ecm is always correcting based off of required torque to meet the rpm demand. So say you are at 20% throttle at 1800rpm, throttle, speed, load, etc. all holding steady and that 20% throttle based off the throttle map is 30mm3, if after all its checks and everything it does that requested fuel amount doesn?t provide the necessary torque to maintain that 1800 rpm, the ecm will adjust and use values from higher quantity cells, say 40mm3. Same goes with as requested fueling is no longer needed to maintain enough torque for an rpm, for example holding the throttle at a steady position while going down a hill, the ecm will adjust for this by lower the actual mm3 as that fueling command from the throttle isn?t needed.

As for smoothing, it just means gentle or smooth looking transitions from one cell to the next. Before worrying about ?smoothing? maps, research more on why you see the hills and valleys in the maps. Some is for meeting emissions requirements and others is for aiding in spooling of the turbo. The goal with timing is to land your peak cylinder pressure from combustion of the fuel just after top dead center. Since you can?t tell when exactly the peak cylinder pressure from combustion is actually taking place without pressure transducers installed in the head for each cylinder, its a bit of a trial and error to find its happy spot which is greatly affected by air temperature, air quantity, fuel temperature, cylinder temperature, fuel pressure and the list goes on and on.